view mercurial/txnutil.py @ 32983:0d757af1ea67

configitems: add a basic class to hold config item information

The goal of this class is allow explicit declaration for the available config
option. This class will hold the data for one specific config item.

To keep it simple we start centralizing the handling of the default config value.

In the future we can expect more data to be carried on this class. For example:
 - documentation,
 - status (experimental, advanced, normal, deprecated),
 - aliases,
 - expected type,
 - etc...

# txnutil.py - transaction related utilities
#
#  Copyright FUJIWARA Katsunori <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

from . import (
    encoding,
)

def mayhavepending(root):
    '''return whether 'root' may have pending changes, which are
    visible to this process.
    '''
    return root == encoding.environ.get('HG_PENDING')

def trypending(root, vfs, filename, **kwargs):
    '''Open  file to be read according to HG_PENDING environment variable

    This opens '.pending' of specified 'filename' only when HG_PENDING
    is equal to 'root'.

    This returns '(fp, is_pending_opened)' tuple.
    '''
    if mayhavepending(root):
        try:
            return (vfs('%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)